/*
 * Copyright 2011-2013 Tyler Blair. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are
 * permitted provided that the following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of
 *       conditions and the following disclaimer.
 *
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list
 *       of conditions and the following disclaimer in the documentation and/or other materials
 *       provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ''AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation are those of the
 * authors and contributors and should not be interpreted as representing official policies,
 * either expressed or implied, of anybody else.
 */
package de.st_ddt.crazyutil.metrics;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.net.Proxy;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.UUID;
import java.util.logging.Level;
import java.util.zip.GZIPOutputStream;

import org.bukkit.Bukkit;
import org.bukkit.configuration.InvalidConfigurationException;
import org.bukkit.configuration.file.YamlConfiguration;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.PluginDescriptionFile;
import org.bukkit.scheduler.BukkitTask;

public class Metrics
{

	/**
	 * The current revision number
	 */
	private final static int REVISION = 7;
	/**
	 * The base url of the metrics domain
	 */
	private static final String BASE_URL = "http://report.mcstats.org";
	/**
	 * The url used to report a server's status
	 */
	private static final String REPORT_URL = "/plugin/%s";
	/**
	 * Interval of time to ping (in minutes)
	 */
	private static final int PING_INTERVAL = 15;
	/**
	 * The plugin this metrics submits for
	 */
	private final Plugin plugin;
	/**
	 * All of the custom graphs to submit to metrics
	 */
	private final Set<Graph> graphs = Collections.synchronizedSet(new HashSet<Graph>());
	/**
	 * The plugin configuration file
	 */
	private final YamlConfiguration configuration;
	/**
	 * The plugin configuration file
	 */
	private final File configurationFile;
	/**
	 * Unique server id
	 */
	private final String guid;
	/**
	 * Debug mode
	 */
	private final boolean debug;
	/**
	 * Lock for synchronization
	 */
	private final Object optOutLock = new Object();
	/**
	 * The scheduled task
	 */
	private volatile BukkitTask task = null;

	public Metrics(final Plugin plugin) throws IOException
	{
		if (plugin == null)
			throw new IllegalArgumentException("Plugin cannot be null");
		this.plugin = plugin;
		// load the config
		configurationFile = getConfigFile();
		configuration = YamlConfiguration.loadConfiguration(configurationFile);
		// add some defaults
		configuration.addDefault("opt-out", false);
		configuration.addDefault("guid", UUID.randomUUID().toString());
		configuration.addDefault("debug", false);
		// Do we need to create the file?
		if (configuration.get("guid", null) == null)
		{
			configuration.options().header("http://mcstats.org").copyDefaults(true);
			configuration.save(configurationFile);
		}
		// Load the guid then
		guid = configuration.getString("guid");
		debug = configuration.getBoolean("debug", false);
	}

	/**
	 * Construct and create a Graph that can be used to separate specific plotters to their own graphs on the metrics website. Plotters can be added to the graph object returned.
	 * 
	 * @param name
	 *            The name of the graph
	 * @return Graph object created. Will never return NULL under normal circumstances unless bad parameters are given
	 */
	public Graph createGraph(final String name)
	{
		if (name == null)
			throw new IllegalArgumentException("Graph name cannot be null");
		// Construct the graph object
		final Graph graph = new Graph(name);
		// Now we can add our graph
		graphs.add(graph);
		// and return back
		return graph;
	}

	/**
	 * Add a Graph object to BukkitMetrics that represents data for the plugin that should be sent to the backend
	 * 
	 * @param graph
	 *            The name of the graph
	 */
	public void addGraph(final Graph graph)
	{
		if (graph == null)
			throw new IllegalArgumentException("Graph cannot be null");
		graphs.add(graph);
	}

	/**
	 * Start measuring statistics. This will immediately create an async repeating task as the plugin and send the initial data to the metrics backend, and then after that it will post in increments of PING_INTERVAL * 1200 ticks.
	 * 
	 * @return True if statistics measuring is running, otherwise false.
	 */
	public boolean start()
	{
		synchronized (optOutLock)
		{
			// Did we opt out?
			if (isOptOut())
				return false;
			// Is metrics already running?
			if (task != null)
				return true;
			// Begin hitting the server with glorious data
			task = plugin.getServer().getScheduler().runTaskTimerAsynchronously(plugin, new Runnable()
			{

				private boolean firstPost = true;

				@Override
				public void run()
				{
					try
					{
						// This has to be synchronized or it can collide with the disable method.
						synchronized (optOutLock)
						{
							// Disable Task, if it is running and the server owner decided to opt-out
							if (isOptOut() && task != null)
							{
								task.cancel();
								task = null;
								// Tell all plotters to stop gathering information.
								for (final Graph graph : graphs)
									graph.onOptOut();
							}
						}
						// We use the inverse of firstPost because if it is the first time we are posting,
						// it is not a interval ping, so it evaluates to FALSE
						// Each time thereafter it will evaluate to TRUE, i.e PING!
						postPlugin(!firstPost);
						// After the first post we set firstPost to false
						// Each post thereafter will be a ping
						firstPost = false;
					}
					catch (final IOException e)
					{
						if (debug)
							Bukkit.getLogger().log(Level.INFO, "[Metrics] " + e.getMessage());
					}
				}
			}, 0, PING_INTERVAL * 1200);
			return true;
		}
	}

	/**
	 * Has the server owner denied plugin metrics?
	 * 
	 * @return true if metrics should be opted out of it
	 */
	public boolean isOptOut()
	{
		synchronized (optOutLock)
		{
			try
			{
				// Reload the metrics file
				configuration.load(getConfigFile());
			}
			catch (final IOException ex)
			{
				if (debug)
					Bukkit.getLogger().log(Level.INFO, "[Metrics] " + ex.getMessage());
				return true;
			}
			catch (final InvalidConfigurationException ex)
			{
				if (debug)
					Bukkit.getLogger().log(Level.INFO, "[Metrics] " + ex.getMessage());
				return true;
			}
			return configuration.getBoolean("opt-out", false);
		}
	}

	/**
	 * Enables metrics for the server by setting "opt-out" to false in the config file and starting the metrics task.
	 * 
	 * @throws java.io.IOException
	 */
	public void enable() throws IOException
	{
		// This has to be synchronized or it can collide with the check in the task.
		synchronized (optOutLock)
		{
			// Check if the server owner has already set opt-out, if not, set it.
			if (isOptOut())
			{
				configuration.set("opt-out", false);
				configuration.save(configurationFile);
			}
			// Enable Task, if it is not running
			if (task == null)
				start();
		}
	}

	/**
	 * Disables metrics for the server by setting "opt-out" to true in the config file and canceling the metrics task.
	 * 
	 * @throws java.io.IOException
	 */
	public void disable() throws IOException
	{
		// This has to be synchronized or it can collide with the check in the task.
		synchronized (optOutLock)
		{
			// Check if the server owner has already set opt-out, if not, set it.
			if (!isOptOut())
			{
				configuration.set("opt-out", true);
				configuration.save(configurationFile);
			}
			// Disable Task, if it is running
			if (task != null)
			{
				task.cancel();
				task = null;
			}
		}
	}

	/**
	 * Gets the File object of the config file that should be used to store data such as the GUID and opt-out status
	 * 
	 * @return the File object for the config file
	 */
	public File getConfigFile()
	{
		// I believe the easiest way to get the base folder (e.g craftbukkit set via -P) for plugins to use
		// is to abuse the plugin object we already have
		// plugin.getDataFolder() => base/plugins/PluginA/
		// pluginsFolder => base/plugins/
		// The base is not necessarily relative to the startup directory.
		final File pluginsFolder = plugin.getDataFolder().getParentFile();
		// return => base/plugins/PluginMetrics/config.yml
		return new File(new File(pluginsFolder, "PluginMetrics"), "config.yml");
	}

	/**
	 * Generic method that posts a plugin to the metrics website
	 */
	private void postPlugin(final boolean isPing) throws IOException
	{
		// Server software specific section
		final PluginDescriptionFile description = plugin.getDescription();
		final String pluginName = description.getName();
		final boolean onlineMode = Bukkit.getServer().getOnlineMode(); // TRUE if online mode is enabled
		final String pluginVersion = description.getVersion();
		final String serverVersion = Bukkit.getVersion();
		final int playersOnline = Bukkit.getServer().getOnlinePlayers().length;
		// END server software specific section -- all code below does not use any code outside of this class / Java
		// Construct the post data
		final StringBuilder json = new StringBuilder(1024);
		json.append('{');
		// The plugin's description file containg all of the plugin data such as name, version, author, etc
		appendJSONPair(json, "guid", guid);
		appendJSONPair(json, "plugin_version", pluginVersion);
		appendJSONPair(json, "server_version", serverVersion);
		appendJSONPair(json, "players_online", Integer.toString(playersOnline));
		// New data as of R6
		final String osname = System.getProperty("os.name");
		String osarch = System.getProperty("os.arch");
		final String osversion = System.getProperty("os.version");
		final String java_version = System.getProperty("java.version");
		final int coreCount = Runtime.getRuntime().availableProcessors();
		// normalize os arch .. amd64 -> x86_64
		if (osarch.equals("amd64"))
			osarch = "x86_64";
		appendJSONPair(json, "osname", osname);
		appendJSONPair(json, "osarch", osarch);
		appendJSONPair(json, "osversion", osversion);
		appendJSONPair(json, "cores", Integer.toString(coreCount));
		appendJSONPair(json, "auth_mode", onlineMode ? "1" : "0");
		appendJSONPair(json, "java_version", java_version);
		// If we're pinging, append it
		if (isPing)
			appendJSONPair(json, "ping", "1");
		if (graphs.size() > 0)
			synchronized (graphs)
			{
				json.append(',');
				json.append('"');
				json.append("graphs");
				json.append('"');
				json.append(':');
				json.append('{');
				boolean firstGraph = true;
				final Iterator<Graph> iter = graphs.iterator();
				while (iter.hasNext())
				{
					final Graph graph = iter.next();
					final StringBuilder graphJson = new StringBuilder();
					graphJson.append('{');
					for (final Plotter plotter : graph.getPlotters())
						appendJSONPair(graphJson, plotter.getColumnName(), Integer.toString(plotter.getValue()));
					graphJson.append('}');
					if (!firstGraph)
						json.append(',');
					json.append(escapeJSON(graph.getName()));
					json.append(':');
					json.append(graphJson);
					firstGraph = false;
				}
				json.append('}');
			}
		// close json
		json.append('}');
		// Create the url
		final URL url = new URL(BASE_URL + String.format(REPORT_URL, urlEncode(pluginName)));
		// Connect to the website
		URLConnection connection;
		// Mineshafter creates a socks proxy, so we can safely bypass it
		// It does not reroute POST requests so we need to go around it
		if (isMineshafterPresent())
			connection = url.openConnection(Proxy.NO_PROXY);
		else
			connection = url.openConnection();
		final byte[] uncompressed = json.toString().getBytes();
		final byte[] compressed = gzip(json.toString());
		// Headers
		connection.addRequestProperty("User-Agent", "MCStats/" + REVISION);
		connection.addRequestProperty("Content-Type", "application/json");
		connection.addRequestProperty("Content-Encoding", "gzip");
		connection.addRequestProperty("Content-Length", Integer.toString(compressed.length));
		connection.addRequestProperty("Accept", "application/json");
		connection.addRequestProperty("Connection", "close");
		connection.setDoOutput(true);
		if (debug)
			System.out.println("[Metrics] Prepared request for " + pluginName + " uncompressed=" + uncompressed.length + " compressed=" + compressed.length);
		// Write the data
		String response;
		try (final OutputStream os = connection.getOutputStream())
		{
			os.write(compressed);
			os.flush();
			// Now read the response
			try (final BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream())))
			{
				response = reader.readLine();
			}
		}
		if (response == null || response.startsWith("ERR") || response.startsWith("7"))
		{
			if (response == null)
				response = "null";
			else if (response.startsWith("7"))
				response = response.substring(response.startsWith("7,") ? 2 : 1);
			throw new IOException(response);
		}
		else // Is this the first update this hour?
		if (response.equals("1") || response.contains("This is your first update this hour"))
			synchronized (graphs)
			{
				final Iterator<Graph> iter = graphs.iterator();
				while (iter.hasNext())
				{
					final Graph graph = iter.next();
					for (final Plotter plotter : graph.getPlotters())
						plotter.reset();
				}
			}
	}

	/**
	 * GZip compress a string of bytes
	 * 
	 * @param input
	 * @return
	 */
	public static byte[] gzip(final String input)
	{
		final ByteArrayOutputStream baos = new ByteArrayOutputStream();
		GZIPOutputStream gzos = null;
		try
		{
			gzos = new GZIPOutputStream(baos);
			gzos.write(input.getBytes("UTF-8"));
		}
		catch (final IOException e)
		{
			e.printStackTrace();
		}
		finally
		{
			if (gzos != null)
				try
				{
					gzos.close();
				}
				catch (final IOException ignore)
				{}
		}
		return baos.toByteArray();
	}

	/**
	 * Check if mineshafter is present. If it is, we need to bypass it to send POST requests
	 * 
	 * @return true if mineshafter is installed on the server
	 */
	private boolean isMineshafterPresent()
	{
		try
		{
			Class.forName("mineshafter.MineServer");
			return true;
		}
		catch (final Exception e)
		{
			return false;
		}
	}

	/**
	 * Appends a json encoded key/value pair to the given string builder.
	 * 
	 * @param json
	 * @param key
	 * @param value
	 * @throws UnsupportedEncodingException
	 */
	private static void appendJSONPair(final StringBuilder json, final String key, final String value) throws UnsupportedEncodingException
	{
		boolean isValueNumeric = false;
		try
		{
			if (value.equals("0") || !value.endsWith("0"))
			{
				Double.parseDouble(value);
				isValueNumeric = true;
			}
		}
		catch (final NumberFormatException e)
		{
			isValueNumeric = false;
		}
		if (json.charAt(json.length() - 1) != '{')
			json.append(',');
		json.append(escapeJSON(key));
		json.append(':');
		if (isValueNumeric)
			json.append(value);
		else
			json.append(escapeJSON(value));
	}

	/**
	 * Escape a string to create a valid JSON string
	 * 
	 * @param text
	 * @return
	 */
	private static String escapeJSON(final String text)
	{
		final StringBuilder builder = new StringBuilder();
		builder.append('"');
		for (int index = 0; index < text.length(); index++)
		{
			final char chr = text.charAt(index);
			switch (chr)
			{
				case '"':
				case '\\':
					builder.append('\\');
					builder.append(chr);
					break;
				case '\b':
					builder.append("\\b");
					break;
				case '\t':
					builder.append("\\t");
					break;
				case '\n':
					builder.append("\\n");
					break;
				case '\r':
					builder.append("\\r");
					break;
				default:
					if (chr < ' ')
					{
						final String t = "000" + Integer.toHexString(chr);
						builder.append("\\u" + t.substring(t.length() - 4));
					}
					else
						builder.append(chr);
					break;
			}
		}
		builder.append('"');
		return builder.toString();
	}

	/**
	 * Encode text as UTF-8
	 * 
	 * @param text
	 *            the text to encode
	 * @return the encoded text, as UTF-8
	 */
	private static String urlEncode(final String text) throws UnsupportedEncodingException
	{
		return URLEncoder.encode(text, "UTF-8");
	}

	/**
	 * Represents a custom graph on the website
	 */
	public static class Graph
	{

		/**
		 * The graph's name, alphanumeric and spaces only :) If it does not comply to the above when submitted, it is rejected
		 */
		private final String name;
		/**
		 * The set of plotters that are contained within this graph
		 */
		private final Set<Plotter> plotters = new LinkedHashSet<Plotter>();

		private Graph(final String name)
		{
			this.name = name;
		}

		/**
		 * Gets the graph's name
		 * 
		 * @return the Graph's name
		 */
		public String getName()
		{
			return name;
		}

		/**
		 * Add a plotter to the graph, which will be used to plot entries
		 * 
		 * @param plotter
		 *            the plotter to add to the graph
		 */
		public void addPlotter(final Plotter plotter)
		{
			plotters.add(plotter);
		}

		/**
		 * Remove a plotter from the graph
		 * 
		 * @param plotter
		 *            the plotter to remove from the graph
		 */
		public void removePlotter(final Plotter plotter)
		{
			plotters.remove(plotter);
		}

		/**
		 * Gets an <b>unmodifiable</b> set of the plotter objects in the graph
		 * 
		 * @return an unmodifiable {@link java.util.Set} of the plotter objects
		 */
		public Set<Plotter> getPlotters()
		{
			return Collections.unmodifiableSet(plotters);
		}

		@Override
		public int hashCode()
		{
			return name.hashCode();
		}

		@Override
		public boolean equals(final Object object)
		{
			if (!(object instanceof Graph))
				return false;
			final Graph graph = (Graph) object;
			return graph.name.equals(name);
		}

		/**
		 * Called when the server owner decides to opt-out of BukkitMetrics while the server is running.
		 */
		protected void onOptOut()
		{
		}
	}

	/**
	 * Interface used to collect custom data for a plugin
	 */
	public static abstract class Plotter
	{

		/**
		 * The plot's name
		 */
		private final String name;

		/**
		 * Construct a plotter with the default plot name
		 */
		public Plotter()
		{
			this("Default");
		}

		/**
		 * Construct a plotter with a specific plot name
		 * 
		 * @param name
		 *            the name of the plotter to use, which will show up on the website
		 */
		public Plotter(final String name)
		{
			this.name = name;
		}

		/**
		 * Get the current value for the plotted point. Since this function defers to an external function it may or may not return immediately thus cannot be guaranteed to be thread friendly or safe. This function can be called from any thread so care should be taken when accessing resources that need to be synchronized.
		 * 
		 * @return the current value for the point to be plotted.
		 */
		public abstract int getValue();

		/**
		 * Get the column name for the plotted point
		 * 
		 * @return the plotted point's column name
		 */
		public String getColumnName()
		{
			return name;
		}

		/**
		 * Called after the website graphs have been updated
		 */
		public void reset()
		{
		}

		@Override
		public int hashCode()
		{
			return getColumnName().hashCode();
		}

		@Override
		public boolean equals(final Object object)
		{
			if (!(object instanceof Plotter))
				return false;
			final Plotter plotter = (Plotter) object;
			return plotter.name.equals(name) && plotter.getValue() == getValue();
		}
	}
}
